XML 22 R112.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Regulatory matters and revenues subject to refund (Details) (USD $) | 0 Months Ended
--- | ---
Dec. 05, 2013 MTPSC [Member] | Apr. 12, 2013 MTPSC [Member] | Sep. 26, 2012 MTPSC [Member] | Nov. 17, 2013 NDPSC [Member] | Oct. 23, 2013 NDPSC [Member] | Sep. 18, 2013 NDPSC [Member] | Oct. 31, 2013 FERC [Member]
Regulatory matters and revenues subject to refund [Line Items] |  |  |  |  |  |  |
Total gas rate increase requested |  |  | $ 3,500,000 |  |  | $ 6,800,000 |
Percent above current rates requested |  |  | 5.90% |  |  | 6.40% |
Amount of requested interim increase in annual gas rates |  |  | 1,700,000 |  |  | 4,500,000 |
Requested percentage of interim gas rate increase |  |  | 2.90% |  |  | 4.20% |
Interim rate increase (decrease), amount |  | 850,000 |  | 4,300,000 | 4,300,000 |  |
Stipulation, amount | 1,500,000 |  |  |  |  |  |
Settlement agreement, amount |  |  |  |  | 4,300,000 |  |
Settlement agreement, percent |  |  |  |  | 4.00% |  |
Rate change application annual increase, amount |  |  |  |  |  |  | 28,900,000
Increased expenditures covered by change application |  |  |  |  |  |  | $ 312,000,000

X
- Definition The amount of requested interim increase in annual gas rates. + References No definition available. + Details
Name: | mdu_AmountOfRequestedInterimIncreaseInAnnualGasRates
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Increased investments covered by change application. + References No definition available. + Details
Name: | mdu_IncreasedInvestments
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition General natural gas rate change application increase, amount. + References No definition available. + Details
Name: | mdu_Ratechangeapplicationannualincreaseamount
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The percentage of interim gas rate increase requested. + References No definition available. + Details
Name: | mdu_RequestedPercentageOfInterimGasRateIncrease
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Settlement agreement that resolved the revenue requirement portion of the application and reflected a natural gas rate increase. + References No definition available. + Details
Name: | mdu_Settlementagreementamount
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Settlement agreement that resolved the revenue requirement portion of the application and reflected a natural gas rate increase, percentage. + References No definition available. + Details
Name: | mdu_Settlementagreementpercent
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Stipulation, amount. + References No definition available. + Details
Name: | mdu_StipulationAmount
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesInterimRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreasePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration